Embodiments of the present invention relate to integrated circuits and the processing for the manufacture of semiconductor devices. More particularly, embodiments of the present invention provide a method and structure for an anti-fuse based non-volatile memory device. Merely by way of example, the present invention provides a method and device for an anti-fuse based programmable serial number generator using conventional CMOS logic process. But it would be recognized that the invention has a much broader range of applicability.
Integrated circuits or “ICs” have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Current ICs provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of ICs. Semiconductor devices are now being fabricated with features less than a quarter of a micron across.
Increasing circuit density has not only improved the complexity and performance of ICs but has also provided lower cost parts to the consumer. An IC fabrication facility can cost hundreds of millions, or even billions, of dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of ICs on it. Therefore, by making the individual devices of an IC smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as each process used in IC fabrication has a limit. That is to say, a given process typically only works down to a certain feature size, and then either the process or the device layout needs to be changed. An example of such a limit is embedded non-volatile memory device used for the manufacture of integrated circuits in a cost effective and efficient way.
Fabrication of custom integrated circuits using chip foundry services has evolved over the years. Fabless chip companies often design the custom integrated circuits. Such custom integrated circuits require a set of custom masks commonly called “reticles” to be manufactured. A chip foundry company called Semiconductor Manufacturing International Corporation (SMIC) of Shanghai, China is an example of a chip company that performs foundry services. Although fabless chip companies and foundry services have increased through the years, many limitations still exist. For example, it is often desirable to incorporate a serial number in an integrated circuit as a security feature. This feature is typically realized using non-volatile memory cells, such as a flash cell. However, it can be expensive to implement this feature in a conventional logic process, such as a CMOS logic process, because new process steps and circuits will be required for high voltage devices and on-chip charge pumps. Alternatives, such as laser fuse devices, are also expensive, because they often require substantial process modification and external equipment, such as a laser writer. These and other limitations are described throughout the present specification and more particularly below.
From the above, it is seen that an improved technique and structure for processing and programming of non-volatile memory devices is desired.